Radiation therapy has been employed to treat tumorous tissue. In radiation therapy, a high energy beam is applied from an external source towards the patient. The external source, which may be rotating (as in the case for arc therapy), produces a collimated beam of radiation that is directed into the patient to the target site. The dose and placement of the dose must be accurately controlled to ensure that the tumor receives sufficient radiation, and that damage to the surrounding healthy tissue is minimized.
Sometimes during a radiation therapy, the patient may undergo movement, such as, breathing motion. In such cases, it may be desirable to determine positions of a moving target such that a radiation beam may be adjusted accordingly to treat the target. Existing techniques for determining a position of an object requires imaging of the object. However, in some cases, the object that is desired to be tracked may not be discernable from the images. This is especially the case when the target that is desired to be tracked is a small cancerous region embedded in some healthy tissue, such as the glandular breast tissue.